Vanishing White Matter Disease Research Articles

Clinical features of 54 cases of leukoencephalopathy with vanishing white matter disease in children

Objective: To summarize the clinical features of leukoencephalopathy with vanishing white matter disease (VWM) in children. Methods: A retrospective cohort study was performed on 54 genetically diagnosed VWM patients in Peking University First Hospital from January 2007 to March 2019. Paper registration form and electronic medical record system were used to collect the data,and the children were divided into five groups according to the age of disease onset:<1 year, 1-<2 years, 2-<4 years, 4-<8 years and 8-<18 years respectively. The progression of motor function, episodic aggravation, epileptic seizures, survival time, brain magnetic resonance imaging (MRI) and genotype features were analyzed and compared. Non-parametric test, χ(2) test or Fisher's exact test were used for comparison among groups; Kaplan-Meier survival curve was adopted to delineate the survival status of the children. Results: Fifty-four VWM patients were included in the study, including 34 males and 20 females.The age of disease onset was 2 years and 8 months (ranged from 6 months to 9 years and 7 months). Onset age was less than 1 year in 5 cases; onset age was 1-<2 years in 12 cases; onset age was 2-<4 years in 25 cases; onset age was 4-<8 years, in 10 cases; onset age was 8-<18 years in 2 cases; 94% (51/54) of patients had complaint of motor regression at the first visit; 87% (47/54) of patients suffered from episodic aggravation. Episodic seizures occurred in 43% (23/54) patients. In survivors with disease durations of 1-3 years, in 38% (9/24) patients the disease was classified as grades Ⅳ-Ⅴ by gross motor function classification system (GMFCS). For the onset age 1-<2 years group, 1 patient was classified as GMFCS Ⅳ among 3 survivors with disease durations of 1-3 years. As for the 2-<4 years group, 6 patients were classified as GMFCS Ⅳ-Ⅴ among 15 patients with disease durations of 1-3 years, whereas 1 patient was classified as GMFCS Ⅳ-Ⅴ among 4 patients with disease durations of 1-3 years in the 4-<8 years group. Lesions, liquefaction and diffusion restriction in brain MRI were compared among different groups, and it was revealed that the earlier the age of disease onset was, the more likely the subcortical white matter (frontal lobe P<0.01,temporal and parieto-occipital lobe both P=0.002), internal capsule (anterior limb P<0.01, posterior limb P=0.00) and brain stem (midbrain P=0.001, pons P<0.01) were to be involved. In addition, internal capsule (anterior limb P=0.002, posterior limb P=0.005) and brain stem (midbrain P=0.001, pons P=0.003) showed more diffuse restricted diffusion. Moreover, the subcortical white matter (frontal and parieto-occipital lobe both P<0.01, temporal lobe P=0.005) showed earlier rarefaction. The 1-year and 2-year survival rates of the overall patients were 81% and 75% respectively, while the 15-year survival rate was 45%. EIF2B5 gene variation was the most common, which accounts for 43% (23/54), followed by EIF2B3 (22%, 12/54). Conclusions: The majority of VWM patients complained of motor regression at the first visit, episodic aggravation and epileptic seizures are common in the course. Earlier age at onset is associated with more rapid clinical progression, shorter survival time as well as more extensive lesions, liquefaction and diffusion restriction in brain MRI. The most common variant gene is EIF2B5, followed by EIF2B3.

Glial pathology in a novel spontaneous mutant mouse of the Eif2b5 gene: a vanishing white matter disease model.

Vanishing white matter disease (VWM) is an autosomal recessive neurological disorder caused by mutation(s) in any subunit of eukaryotic translation initiation factor 2B (eIF2B), an activator of translation initiation factor eIF2. VWM occurs with mutation of the genes encoding eIF2B subunits (EIF2B1, EIF2B2, EIF2B3, EIF2B4, and EIF2B5). However, little is known regarding the underlying pathogenetic mechanisms or how to treat patients with VWM. Here we describe the identification and detailed analysis of a new spontaneous mutant mouse harboring a point mutation in the Eif2b5 gene (p.Ile98Met). Homozygous Eif2b5I98M mutant mice exhibited a small body, abnormal gait, male and female infertility, epileptic seizures, and a shortened lifespan. Biochemical analyses indicated that the mutant eIF2B protein with the Eif2b5I98M mutation decreased guanine nucleotide exchange activity on eIF2, and the level of the endoplasmic reticulum stress marker activating transcription factor 4 was elevated in the 1-month-old Eif2b5I98M brain. Histological analyses indicated up-regulated glial fibrillary acidic protein immunoreactivity in the astrocytes of the Eif2b5I98M forebrain and translocation of Bergmann glia in the Eif2b5I98M cerebellum, as well as increased mRNA expression of an endoplasmic reticulum stress marker, C/EBP homologous protein. Disruption of myelin and clustering of oligodendrocyte progenitor cells were also indicated in the white matter of the Eif2b5I98M spinal cord at 8months old. Our data show that Eif2b5I98M mutants are a good model for understanding VWM pathogenesis and therapy development. Cover Image for this issue: doi: 10.1111/jnc.14751.

Astrocyte Subtype Vulnerability in Stem Cell Models of Vanishing White Matter.

ObjectiveAstrocytes have gained attention as important players in neurological disease. In line with their heterogeneous character, defects in specific astrocyte subtypes have been identified. Leukodystrophy vanishing white matter (VWM) shows selective vulnerability in white matter astrocytes, but the underlying mechanisms remain unclear. Induced pluripotent stem cell technology is being extensively explored in studies of pathophysiology and regenerative medicine. However, models for distinct astrocyte subtypes for VWM are lacking, thereby hampering identification of disease‐specific pathways.MethodsHere, we characterize human and mouse pluripotent stem cell–derived gray and white matter astrocyte subtypes to generate an in vitro VWM model. We examined morphology and functionality, and used coculture methods, high‐content microscopy, and RNA sequencing to study VWM cultures.ResultsWe found intrinsic vulnerability in specific astrocyte subpopulations in VWM. When comparing VWM and control cultures, white matter–like astrocytes inhibited oligodendrocyte maturation, and showed affected pathways in both human and mouse cultures, involving the immune system and extracellular matrix. Interestingly, human white matter–like astrocytes presented additional, human‐specific disease mechanisms, such as neuronal and mitochondrial functioning.InterpretationAstrocyte subtype cultures revealed disease‐specific pathways in VWM. Cross‐validation of human‐ and mouse‐derived protocols identified human‐specific disease aspects. This study provides new insights into VWM disease mechanisms, which helps the development of in vivo regenerative applications, and we further present strategies to study astrocyte subtype vulnerability in neurological disease. ANN NEUROL 2019;86:780–792

Adult-onset vanishing white matter disease with the EIF2B2 gene mutation presenting as menometrorrhagia

BackgroundVanishing white matter disease (VWMD) is one of the most prevalent inherited leukoencephalopathies, which generally presents in childhood as a progressive disorder while less beginning in adulthood. The present report describes the clinical, neuroimaging, and genetic findings of a female patient with adult-onset VWMD. In addition, to provide a clearer delineation of the clinical and genetic characteristics of female adult-onset VWMD patients, 32 genetically confirmed female adult-onset EIF2B-mutated cases are summarized.Case presentationThe patient described here suffered from long-term menometrorrhagia prior to manifesting progressive neurological impairments that included tremors, bilateral pyramidal tract injury, cerebellar ataxia, and dementia. To the best of our knowledge, this is the first female patient with adult-onset VWMD suffering from long-term menometrorrhagia attributed to the c.254 T > A and c.496A > G mutations in the EIF2B2 gene; the c.496A > G mutation has not been reported in previous studies. The patient also exhibited metabolic dysfunction. The present findings widen the spectrum of phenotypic heterogeneity observed in VWMD patients.ConclusionsThe present report summarizes 33 female patients with adult-onset VWMD to provide an overview of the clinical and genetic characteristics of this disorder and ovarioleukodystrophy. The mean age of clinical onset in female patients with adult-onset VWMD was 36.8 years and the neurological symptoms primarily included motor and cognitive dysfunction such as paraparesis, cerebellar ataxia, and executive deficits. In addition, ovarian failure occurred in all of these female patients and usually preceded the neurological symptoms. Furthermore, several patients also suffered from metabolic dysfunction. All 33 patients had mutations on EIF2B1–5, and of these, the c.338 G > A mutation in the EIF2B5 gene (p.Arg113His) was the most common. These findings suggest that clinicians should be aware of adult-onset forms of VWMD as well as its typical magnetic resonance imaging (MRI) and clinical characteristics although this pathology is usually recognized as a pediatric disorder. No curative treatment is presently available, and thus early recognition is important to prevent triggering events and to allow for genetic counseling.

Vanishing white matter disease with different faces.

The goal of this study was to better understand vanishing white matter (VWM) disease, which is one of the most common hereditary white matter disorders, and its relationship to radiologic features, genetic analyses, and clinical findings. We performed a study on 11 patients to describe the clinical and neuroimaging features of VWM. Patients were grouped into "infantile," "early childhood," and "juvenile" based on their onset age. EIF2B1-5 genes encoding five subunits of eukaryotic translation initiation factor 2B (eIF2B) were analyzed in all patients with clinically suspected VWM disease. In brain magnetic resonance imaging (MRI), all patients showed white matter abnormalities with various degrees. The initial clinical presentation in five of patients was ataxia, with severe refractory epilepsy in three patients. In children with infantile-onset VWM, a rapid deterioration of motor function was detected, and the frequency of epilepsy was higher. Two patients showed manifestations of end-stage VWM disease, and one of them had chronic subdural hematoma. One of our patients and his father were diagnosed with Brugada syndrome. Sequencing of the exons and exon-intron boundaries of the EIF2B1-5 genes revealed mutations in the genes EIF2B5 (5 cases), EIF2B3 (3 cases), and EIF2B4 (2 cases). We also found a novel mutation in one patient: c.323_325delGAA in the EIF2B1 gene. In this study, in addition to classical clinical and radiological findings, we wanted to emphasize that we may be confronted with refractory epilepsy (early infancy), cardiac problems, and intracranial complications that may occur in advanced stages.

EIF2B Mutations Cause Mitochondrial Malfunction in Oligodendrocytes.

Vanishing white matter (VWM) disease (OMIM#306896) is an autosomal recessive neurodegenerative leukodystrophy caused by hypomorphic mutations in any of the five genes encoding the subunits of eukaryotic translation initiation factor 2B (eIF2B). The disease is manifested by loss of cerebral white matter and progressive deterioration upon exposure to environmental and physiological stressors. "Foamy" oligodendrocytes (OLG), increased numbers of oligodendrocytes precursor cells (OPC), and immature defective astrocytes are major neuropathological denominators. Our recent work using Eif2b5R132H/R132H mice uncovered a fundamental link between eIF2B and mitochondrial function. A decrease in oxidative phosphorylation capacity was observed in mutant astrocytes and fibroblasts. While an adaptive increase in mitochondria abundance corrects the phenotype of mutant fibroblasts, it is not sufficient to compensate for the high-energy demand of astrocytes, explaining their involvement in the disease. To date, astrocytes are marked as central for the disease while eIF2B-mutant OLG are currently assumed to lack a cellular phenotype on their own. Here we show a reduced capacity of eIF2B-mutant OPC isolated from Eif2b5R132H/R132H mice to conduct oxidative respiration despite the adaptive increase in their mitochondrial abundance. We also show their impaired ability to efficiently complete critical differentiation steps towards mature OLG. The concept that defective differentiation of eIF2B-mutant OPC could be a consequence of mitochondrial malfunction is in agreement with numerous studies indicating high dependency of differentiating OLG on accurate mitochondrial performance and ATP availability.

Vanishing white matter disease in adulthood

Vanishing white matter disease in adulthood

Modeling vanishing white matter disease with patient-derived induced pluripotent stem cells reveals astrocytic dysfunction.

SummaryAimsVanishing white matter disease (VWM) is an inherited leukoencephalopathy in children attributed to mutations in EIF2B1–5, encoding five subunits of eukaryotic translation initiation factor 2B (eIF2B). Although the defects are in the housekeeping genes, glial cells are selectively involved in VWM. Several studies have suggested that astrocytes are central in the pathogenesis of VWM. However, the exact pathomechanism remains unknown, and no model for VWM induced pluripotent stem cells (iPSCs) has been established.MethodsFibroblasts from two VWM children were reprogrammed into iPSCs by using a virus‐free nonintegrating episomal vector system. Control and VWM iPSCs were sequentially differentiated into neural stem cells (NSCs) and then into neural cells, including neurons, oligodendrocytes (OLs), and astrocytes.ResultsVanishing white matter disease iPSC‐derived NSCs can normally differentiate into neurons, oligodendrocytes precursor cells (OPCs), and oligodendrocytes in vitro. By contrast, VWM astrocytes were dysmorphic and characterized by shorter processes. Moreover, δ‐GFAP and αB‐Crystalline were significantly increased in addition to increased early and total apoptosis.ConclusionThe results provided further evidence supporting the central role of astrocytic dysfunction. The establishment of VWM‐specific iPSC models provides a platform for exploring the pathogenesis of VWM and future drug screening.

Non-multiple-Sclerosis-Related Typical and Atypical White Matter Disorders: Our Experience in the Last 2 Years in Both Children and Adults From a Tertiary Care Center in India.

Introduction:White matter signal changes are common in wide spectrum of disorders other than primary demyelinating diseases. Knowledge into their characteristics is of great relevance as treatment options are available in most cases, if diagnosed early.Patient and methods:Patients both children and adults who showed radiological evidences of leukoencephalopathy which was not due to primary demyelinating disorders were evaluated in detail.Results:There were a total of 55 patients in the last 2 years. 58% patients were <10 years, 16% were <20years, 9% were <30 years and the rest of the patients were 40 and above. Commonest condition was ALD, followed by SSPE and Unclassified group. There were 3 cases each of MLD, Krabbe’s, Vanishing White Matter Disease and Hypomyelination.Discussion and Conclusion:White matter disorders belong to a wide spectrum of illnesses which varies from degeneration to a spectrum of other disorders. Correlating the clinical, radiological and other laboratory data are mandatory for proper diagnosis. Those who belong to older age with shorter duration and uncharacterized radiological features suffered from acquired treatable causes.

Drug Screening Identifies Sigma-1-Receptor as a Target for the Therapy of VWM Leukodystrophy.

Vanishing white matter (VWM) disease is an autosomal genetic leukodystrophy caused by mutations in subunits of eukaryotic translation initiation factor 2B (eIF2B). The clinical symptoms exhibit progressive loss of white matter in both hemispheres of the brain, accompanied by motor functions deterioration, neurological deficits, and early death. To date there is no treatment for VWM disease. The aim of this work was to expedite rational development of a therapeutic opportunity. Our approach was to design a computer-aided strategy for an efficient and reliable screening of drug-like molecules; and to use primary cultures of fibroblasts isolated from the Eif2b5R132H/R132H VWM mouse model for screening. The abnormal mitochondria content phenotype of the mutant cells was chosen as a read-out for a simple cell-based fluorescent assay to assess the effect of the tested compounds. We obtained a hit rate of 0.04% (20 hits out of 50,000 compounds from the selected library). All primary hits decreased mitochondria content and brought it closer to WT levels. Structural similarities between our primary hits and other compounds with known targets allowed the identification of three putative cellular pathways/targets: 11β-hydroxysteroid dehydrogenase type 1, Sonic hedgehog (Shh), and Sigma-1-Receptor (S1R). In addition to initial experimental indication of Shh pathway impairment in VWM mouse brains, the current study provides evidence that S1R is a relevant target for pharmaceutical intervention for potential treatment of the disease. Specifically, we found lower expression level of S1R protein in fibroblasts, astrocytes, and whole brains isolated from Eif2b5R132H/R132H compared to WT mice, and confirmed that one of the hits is a direct binder of S1R, acting as agonist. Furthermore, we provide evidence that treatment of mutant mouse fibroblasts and astrocytes with various S1R agonists corrects the functional impairments of their mitochondria and prevents their need to increase their mitochondria content for compensation purposes. Moreover, S1R activation enhances the survival rate of mutant cells under ER stress conditions, bringing it to WT levels. This study marks S1R as a target for drug development toward treatment of VWM disease. Moreover, it further establishes the important connection between white matter well-being and S1R-mediated proper mitochondria/ER function.

A Promising Small Molecule for Vanishing White Matter Disease.

Investigators from Calico Life Sciences LLC and AbbVie report the effects of a novel drug targeting the genetic basis of Vanishing White Matter Disease (VWMD).

Analysis of eIF2B bodies and their relationships with stress granules and P-bodies

Eukaryotic cells respond to stress and changes in the environment in part by repressing translation and forming cytoplasmic assemblies called stress granules and P-bodies, which harbor non-translating mRNAs and proteins. A third, but poorly understood, assembly called the eIF2B body can form and contains the eIF2B complex, an essential guanine exchange factor for the translation initiation factor eIF2. Hypomorphic EIF2B alleles can lead to Vanishing White Matter Disease (VWMD), a leukodystrophy that causes progressive white matter loss. An unexplored question is how eIF2B body formation is controlled and whether VWMD alleles in EIF2B alter the formation of eIF2B bodies, stress granules, or P-bodies. To examine these issues, we assessed eIF2B body, stress granule, and P-body induction in wild-type yeast cells and cells carrying VWMD alleles in the EIF2B2 (GCD7) and EIF2B5 (GCD6) subunits of eIF2B. We demonstrate eIF2B bodies are rapidly and reversibly formed independently of stress granules during acute glucose deprivation. VWMD mutations had diverse effects on stress-induced assemblies with some alleles altering eIF2B bodies, and others leading to increased P-body formation. Moreover, some VWMD-causing mutations in GCD7 caused hyper-sensitivity to chronic GCN2 activation, consistent with VWMD mutations causing hyper-sensitivity to eIF2α phosphorylation and thereby impacting VWMD pathogenesis.

Natural History of Vanishing White Matter.

ObjectiveTo comprehensively describe the natural history of vanishing white matter (VWM), aiming at improving counseling of patients/families and providing natural history data for future therapeutic trials.MethodsWe performed a longitudinal multicenter study among 296 genetically confirmed VWM patients. Clinical information was obtained via disease‐specific clinical questionnaire, Health Utilities Index and Guy's Neurological Disability Scale assessments, and chart review.ResultsFirst disease signs occurred at a median age of 3 years (mode = 2 years, range = before birth to 54 years); 60% of patients were symptomatic before the age of 4 years. The nature of the first signs varied for different ages of onset. Overall, motor problems were the most common presenting sign, especially in children. Adolescent and adult onset patients were more likely to exhibit cognitive problems early after disease onset. One hundred two patients were deceased. Multivariate Cox regression analysis revealed a positive relation between age at onset and both preservation of ambulation and survival. Absence of stress‐provoked episodes and absence of seizures predicted more favorable outcome. In patients with onset before 4 years, earlier onset was associated with more severe disability and higher mortality. For onset from 4 years on, disease course was generally milder, with a wide variation in severity. There were no significant differences for sex or for the 5 eIF2B gene groups. The results confirm the presence of a genotype–phenotype correlation.InterpretationThe VWM disease spectrum consists of a continuum with extremely wide variability. Age at onset is a strong predictor for disease course. Ann Neurol 2018;84:274–288

Case Report: Cerebral leukodystrophy and the gonadal endocrinopathy: a rare but real association

A 30 year old married Pakistani woman presented in January 2018 with an eight month history of progressive left sided weakness, ataxia, spasticity, underdeveloped secondary sexual characteristics and primary infertility. She was the elder sister of a 19 year old bed bound woman who was diagnosed with vanishing white matter (VWM) disease 12 months previously. The MRI scan of the brain demonstrated diffuse leukodystrophy and her hormonal assays were significant for premature ovarian insufficiency. Results from her genetic tests demonstrated a point mutation in eukaryotic initiation factor 2B (EIF2B). Thus, she was the second confirmed case of VWM from her family of 12 siblings with normal parents.

EIF2B2 mutations in vanishing white matter disease hypersuppress translation and delay recovery during the integrated stress response.

Mutations in eIF2B genes cause vanishing white matter disease (VWMD), a fatal leukodystrophy that can manifest following physical trauma or illness, conditions that activate the integrated stress response (ISR). EIF2B is the guanine exchange factor for eIF2, facilitating ternary complex formation and translation initiation. During the ISR, eIF2α is phosphorylated and inhibits eIF2B, causing global translation suppression and stress-induced gene translation, allowing stress adaptation and recovery. We demonstrate that VWMD patient cells hypersuppress translation during the ISR caused by acute ER stress, delaying stress-induced gene expression and interrupting a negative feedback loop that allows translational recovery by GADD34-mediated dephosphorylation of phospho-eIF2α. Thus, cells from VWMD patients undergo a prolonged state of translational hyperrepression and fail to recover from stress. We demonstrate that small molecules targeting eIF2B or the eIF2α kinase PERK rescue translation defects in patient cells. Therefore, defects in the ISR could contribute to white matter loss in VWMD.

The small molecule ISRIB rescues the stability and activity of Vanishing White Matter Disease eIF2B mutant complexes.

eIF2B is a dedicated guanine nucleotide exchange factor for eIF2, the GTPase that is essential to initiate mRNA translation. The integrated stress response (ISR) signaling pathway inhibits eIF2B activity, attenuates global protein synthesis and upregulates a set of stress-response proteins. Partial loss-of-function mutations in eIF2B cause a neurodegenerative disorder called Vanishing White Matter Disease (VWMD). Previously, we showed that the small molecule ISRIB is a specific activator of eIF2B (<xref ref-type="bibr" rid="bib38">Sidrauski et al., 2015</xref>). Here, we report that various VWMD mutations destabilize the decameric eIF2B holoenzyme and impair its enzymatic activity. ISRIB stabilizes VWMD mutant eIF2B in the decameric form and restores the residual catalytic activity to wild-type levels. Moreover, ISRIB blocks activation of the ISR in cells carrying these mutations. As such, ISRIB promises to be an invaluable tool in proof-of-concept studies aiming to ameliorate defects resulting from inappropriate or pathological activation of the ISR.

Case Report: Cerebral leukodystrophy and the gonadal endocrinopathy: a rare but real association.

A 30 year old married Pakistani woman presented in January 2018 with an eight month history of progressive left sided weakness, ataxia, spasticity, underdeveloped secondary sexual characteristics and primary infertility. She was the elder sister of a 19 year old bed bound woman who was diagnosed with vanishing white matter (VWM) disease 12 months previously. The MRI scan of the brain demonstrated diffuse leukodystrophy and her hormonal assays were significant for premature ovarian failure. Results from her genetic tests demonstrated a point mutation in eukaryotic initiation factor 2B (EIF2B). Thus, she was the second confirmed case of VWM from her family of 12 siblings with normal parents.

Adult-Onset Leukoencephalopathy with Vanishing White Matter

Leukoencephalopathy with vanishing white matter (LEVWM) is one of the most common hereditary leukoencephalopathies with characteristic MRI picture of diffuse white matter lesions with cystic degeneration. The disease is associated with EIF2B1-5 genes, encoding five subunits of translation initiation factor EIF2B. There are infantile, Childhood (the most frequent one), and adult-onset forms. Adult-onset LEVWM accounts for 15–20% of all cases and is characterized by significant clinical variability. In addition to neurological and cognitive disorders, this disease is characterized by ovarian failure. The review presents the clinical and molecular genetic aspects of adult-onset LEVWM.

Role of Saccharomyces cerevisiae TAN1 (tRNA acetyltransferase) in eukaryotic initiation factor 2B (eIF2B)-mediated translation control and stress response.

Eukaryotic initiation factor 2B (eIF2B) controls the first step of translation by catalyzing guanine nucleotide exchange on eukaryotic initiation factor 2 (eIF2). Mutations in the genes encoding eIF2B subunits inhibit the nucleotide exchange and eventually slow down the process of translation, causing vanishing white matter disease. We constructed a Saccharomyces cerevisiae genomic DNA library in YEp24 vector and screened it for the identification of extragenic suppressors of eIF2B mutations, corresponding to human eIF2B mutations. We found a suppressor-II (Sup-II) genomic clone, as suppressor of eIF2Bβ (gcd7-201) mutation. Identification of Sup-II reveals the presence of truncated SEC15, full-length TAN1 (tRNA acetyltransferase), full-length EMC4, full-length YGL230C (putative protein) and truncated SAP4 genes. Full-length TAN1 (tRNA acetyltransferase) gene, subcloned into pEG(KG) vector and overexpressed in gcd7-201 gcn2∆ strain, suppresses the slow-growth (Slg-) and general control derepression (Gcd-) phenotype of gcd7-201 gcn2∆ mutation, but YGL230C did not show any effect. A GST-Tan1p fusion protein of 60kDa was detected by western blotting using α-GST antibodies. Interestingly, Tan1p overexpression also suppresses the temperature-sensitive (Ts-), Slg- and Gcd- phenotype of eIF2Bγ (gcd1-502) mutant. Role of Tan1p protein in eIF2B-mediated translation regulation was also studied. Results revealed that Tan1p overexpression confers resistance to GCD7 GCN2, gcd7-201 gcn2∆, GCD7 gcn2∆ growth defect under ethanol, H2O2 and caffeine stress. No resistance to DMSO-, NaCl- and DTT-mediated growth defect upon GCD7 gcn2∆, GCD7 GCN2, gcd7-201 gcn2∆ was observed by overexpression of TAN1. Hence, we proposed that Tan1p is involved directly or indirectly in regulating eIF2B-mediated translation.

Mutant eIF2B leads to impaired mitochondrial oxidative phosphorylation in vanishing white matter disease.

Eukaryotic translation initiation factor 2B (eIF2B) is a master regulator of protein synthesis under normal and stress conditions. Mutations in any of the five genes encoding its subunits lead to vanishing white matter (VWM) disease, a recessive genetic deadly illness caused by progressive loss of white matter in the brain. In this study we used fibroblasts, which are not involved in the disease, to demonstrate the involvement of eIF2B in mitochondrial function and abundance. Mass spectrometry of total proteome of mouse embryonic fibroblasts (MEFs) isolated from Eif2b5R132H/R132H mice revealed unbalanced stoichiometry of proteins involved in oxidative phosphorylation and of mitochondrial translation machinery components, among others. Mutant MEFs exhibit 55% decrease in oxygen consumption rate per mtDNA content and 47% increase in mitochondrial abundance (p<0.005), reflecting adaptation to energy requirements. A more robust eIF2B-associated oxidative respiration deficiency was found in mutant primary astrocytes, which exhibit >3-fold lower ATP-linked respiration per cell despite a 2-fold increase in mtDNA content (p<0.03). The 2-fold increase in basal and stimulated glycolysis in mutant astrocytes (p≤0.03), but not in MEFs, demonstrates their higher energetic needs and further explicates their involvement in the disease. The data demonstrate the critical role of eIF2B in tight coordination of expression from nuclear and mitochondrial genomes and illuminates the importance of mitochondrial function in VWM pathology. Further dissection of the signaling network associated with eIF2B function will help generating therapeutic strategies for VWM disease and possibly other neurodegenerative disorders.